Clinical and pathophysiological significance of anti-neutrophil cytoplasmic autoantibodies in vasculitis syndromes

Necrotizing vasculitis of small blood vessels is a rare condition, but when it affects important organs it can lead to life-threatening organ damage and death. Thus, recognizing these conditions at an early stage before they spread to become systemic is a constant challenge to clinical medicine. The objectives of this review are: to give advice on clinical indications for ANCA diagnostics and laboratory procedures for highly specifically detecting the most important ANCA; to provide some data on the autoantigens involved in ANCA reactivity in small vessel vasculitides; and to discuss at the occurrence of ANCA in different vasculitic populations and at different stages of disease. One important task for the near future will be to standardize the assays used for ANCA detection/quantification and to harmonize the results given to clinicians by ensuring that international reference reagents are used by laboratories and the diagnostic industry. Finally, the author has attempted to summarize the role that ANCA are currently believed to play in the immuno-inflammatory events that take place in tissues and that affect small vessels in idiopathic vasculitis. The review concludes that the presence of ANCA is likely to become an important criterion for diagnosing idiopathic small vessel vasculitis.